colored rectangular areas in a bitmap - how?

[Chris Holbrook]

see source code forum for implementation of "Dirty Rectangles": http://www.powerbasic.com/support/pb...291#post309291

[Chris Holbrook]

"Dirty Rectangles"

Thanks Chris, I am investigating. It is much faster.

**** added - there is a very useful tutorial here: http://www.codeproject.com/KB/GDI/updatergn.aspx

[Chris Boss]

The solution is a technique called "Dirty Rectangles"!

When only small portions of the screen are being updated quickly, you can define a region (multiple rectangles combined) which contains only the area which needs to be repainted.

Create a region and then add every area you plan to update (you draw on) to the region to create a complex region.

Then call InvalidateRgn to make windows repaint only that region.

Using dirty rectangles can increase the update speed significantly depending upon how much area is being updated.

[Michael Mattias]

FillRect()

[Chris Holbrook]

use GRAPHIC BOX?

fonely. I'm doing it to replace GRAPHIC BOX, which mixes but poorly with subclassing.

[Chris Holbrook]

So far...

This code draws a box with the specified line and fill colors on a DC - a memory DC in the application, then triggers WM_PAINT in the target control, and WM_PAINT does the rest. Can it be done better/faster?

'---------------------------------------------------------------------
sub MyDrawBox ( hDC as dword,  lX as long, lY as long, lW as long, lH as long, lBoxColor as long, lBGColor as long)
    local hOldPen, holdBrush, hbrush as dword
    local r as rect
    
    holdbrush = selectobject(hdc, CreateSolidBrush(lBGColor))
    setrect byval varptr(r), lX, lY, lX + lW, lY + lH
    hOldPen   = SelectObject(hDC, CreatePen(%PS_SOLID, 1, lBoxColor))
    rectangle hDC, lX, lY, lX + lW, lY + lH
    DeleteObject SelectObject(hDC, hOldPen)
    DeleteObject selectobject(hdc, holdbrush)
    invalidaterect ghStatic, byval varptr(r), 1
end sub
'-------------------------------------------------------------------------
(wndproc)
....
        case %wm_paint
            hDC = BeginPaint(ghStatic, PS)
            bitblt HDC, 0, 0, PS.rcPaint.nright - PS.rcPaint.nleft, _
                              PS.rcPaint.nbottom - PS.rcPaint.ntop, gHCDC, 0, 0, %SRCCOPY
            endpaint ghStatic, ps

*** later: changed first two coordiante parameters in Bitblt for PS.rcPaint.nleft, PS.rcPaint.ntop and it made no difference at all. Does this mean that the PS.rcPaint rect is the same as the whole client rect, even though I only invalidated a little bit of it?

*** later yet: yes, the whole of the client gets invalidated. Why? How to code around this - a global changedrect?

[Paul Dixon]

Chris,
use GRAPHIC BOX?

'PBCC5 program
#BREAK ON
FUNCTION PBMAIN () AS LONG
GRAPHIC WINDOW "Rectangles",1,1,400,400 TO hWin???
GRAPHIC ATTACH hWin???,0

FOR r&=1 TO 200 STEP 5
    FillColour&=r&*2+256
    GRAPHIC BOX (r&*2,r&*3) - (r&*4,r&*5) ,,%RED,FillColour&
NEXT
          
WAITKEY$

END FUNCTION

Paul.

[Chris Holbrook]

How should I create colored rectangular areas in a bitmap, please? The speed of execution is important, BTW.